Method for producing nanosilver on a large scale, method for manufacturing nanosilver-adsorbed fiber, and antibacterial fiber thereby

ABSTRACT

A method for producing nanosilver on a large scale, a method of manufacturing nanosilver-adsorbed fiber, and an antibacterial fiber manufactured thereby. The nanosilver having a size of 5 nm or less can be generated on a large scale by controlling a minutely electronic current between the two Ag electrodes in a water electrolysis system, while a voltage of 10,000˜300,000 is applied to two Ag electrodes. The nanosilver-adsorbed fiber is manufactured by applying the aqueous solution containing nanosilver to the surface of the synthetic fibers; adsorbing the nanosilver onto the synthetic fibers using a process selected from the group consisting of thermal fixation, high frequency radiation, bubbling, and combinations thereof; and conducting post-finishing at 160 to 200° C.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a method for producing nanosilver on alarge scale, a method of manufacturing nanosilver-adsorbed fiber, andantibacterial fiber manufactured thereby. More particularly, the presentinvention relates to the method for producing nanosilver on a largescale having a size of 5 nm or lower by allowing only a minute electriccurrent to flow between two opposite silver electrodes in the presenceof a high voltage in a water electrolysis system, a method ofmanufacturing nanosilver-adsorbed fiber by taking advantage of thebetter applicability of smaller silver particles, and an antibacterialfiber manufactured thereby.

2. Description of the Prior Art

A variety of microbes are found in large quantities in daily livingenvironments. Particularly, they grow and proliferate on clothes andform flora even on the skin. The microbes degrade fibers or digestnutrients in sweat or contaminants, producing bad odors or causing greatdamage to the health of humans.

WHO reports that microbial contamination corresponds to about 30% of themortality in the world. Unfortunately, current scientific technologiesfall short of sufficiently controlling harmful microbes.

Therefore, it is intensively researched to developantimicrobial/germicidal agents or products that are satisfied withharmless to human bodies and have improved functionality.

As representative example of the antimicrobial agents, it is known thatsilver can absolutely suppress almost all single cell pathogens. Becauseof such antimicrobial activity, silver has been used long and widely inantimicrobial fields, for example, tableware, such as bowls, spoons,chopsticks, etc., and herbal medicines such as silver-coated pills.

As for the antibacterial function of silver, it is reportedly based onthe activity of suppressing certain enzymatic reactions essential forthe metabolism of pathogens, thus killing them.

Particularly in association with nano technology, silver in a nano stateexhibits more powerful antibacterial and germicidal activity. Manyresearch results report that silver in a nano state can kill as many as650 kinds of bacteria and other microbes and show powerful suppressionagainst fungi.

In addition, the smaller silver particles are, the more powerfulantibacterial/germicidal activity, because silver becomes to theincrease in surface area.

According to experimental data, silver powders show 99.9% antibacterialand germicidal efficiency over a variety of bacteria, includingenterobacteria, Staphylococcus aureus, Salmonella, Vibrio, shigella,Pneumococcus, typoid, and even MRSA (methicillin resistantStaphylococcus aureus). That means that almost no bacteria can survive 5minutes or longer in contact with nanosilver.

While having tenfold more potent suppression against bacteria than theconventional chloride-based agent, a nanosilver does not damage humanbodies at all. Therefore it is expected to be a useful therapeutic agentagainst various inflammations. In addition, taking advantage ofnanosilver, various functional products having antibacterial anddeodorizing activities are on the market.

In the fiber and textile industries, accordingly, it is key point toproduce nanosilver having such excellent effects on a large scale and toeffectively intercalate the nanosilver into fibers.

In past three decades, synthetic fibers have been used in a wide rangeof fields of human life as complements to or substitutes for naturalfibers and even as materials that are functionally superior to naturalfibers. During this period, synthetic fibers for clothes have beendeveloped towards practicality, comfort, and other functionalities.Furthermore, it has been actively researched to environment- andbody-friendly synthetic fibers in recent. In a persistent effort todevelop synthetic fibers that satisfy the above request, theantibacterial activity of nanosilver is applied to fibers.

Conventionally, nanosilver has been extracted using a physical method,such as liquid phase reduction, grinding, etc., or an electrolyticmethod. The electrolytic method is conducted under low temperature andvoltage that silver having 99.9% of contents is added to distilledwater, and then the silver-containing compounds are electrolyzed andcarried to electrophoresis through the (+) and (−) of each molecule,results in collecting nanosilver.

On the other hand, as a representative method to intercalate nanosilverinto fibers, synthetic fibers are manufactured by mixing nanosilver withraw synthetic fiber materials before the synthetic fibers are spun.However, the fibers, which are synthesized in the above mentionedmethod, is poor in antibacterial or germicidal activity because mostsilver is deeply intercalated into synthetic fibers while only a smallamount of silver is exposed on the surfaces of synthetic fibers.

Alternatively, antibacterial agents, such as silver, silver oxide,nanosilver etc., are coated onto synthetic fibers. However, theantibacterial agents have poor adhesive strength with synthetic fibers;therefore the synthetic fibers are inferior to washing durability.

Leading to the present invention, intensive and thorough research,conducted by the present inventors, on antibacterial fibers and clothresulted in the finding that nanosilver must be exposed in a largeramount on the surface of synthetic fibers, rather than be embeddedwithin them, in order to maximize the germicidal or antibacterial effectof silver. The smaller the synthetic fibers are, the more powerfulantibacterial/germicidal activities are. Also, In order to obtain thesmaller nanosilver, it is designed that the mass production ofnanosilver is generated by keeping up with minute electronic currentbetween the two Ag electrodes in water electrolysis system to highvoltage.

SUMMARY OF THE INVENTION

It is an aspect of the present invention to provide a method forproducing nanosilver on a large scale.

It is another aspect of the present invention to provide a method formanufacturing nanosilver-adsorbed fiber that nanosilver is intensivelyadsorbed on surface of synthetic fibers.

It is another aspect of the present invention to provide anantibacterial fiber manufactured thereby.

In an exemplary embodiment of the present invention, a method forproducing nanosilver on a large scale is provided. More practically, thenanosilver on a large scale is generated by controlling a minutelyelectronic current between the two Ag electrodes in water electrolysissystem, while a voltage of 10,000˜300,000 is applied to two Agelectrodes.

An object of the invention is to provide a nanosilver on a large scale,preferably comprising; loading water so as to immerse the two Agelectrode plates in the water electrolysis system, applying voltage of10,000˜300,000 to two Ag electrodes, moving the circuit breaker upwardsor downwards relative to the voltage, and thus controlling minutelyelectric current between the two Ag electrodes. The water electrolysissystem preferably comprises: a water reservoir provided with a waterinlet valve for introducing water thereinto and a water outlet valve fordraining the water therefrom; the two Ag electrode plates connected to aDC+ electric power source and a DC− electric power source respectively,the two Ag electrodes being provided on respective opposite sides of thewater reservoir; a circuit breaker for dividing the water reservoir intotwo sections, and being provided in a middle of the water reservoir; anda groove for the circuit breaker, being formed in a middle portion ofthe water reservoir.

The particle size of the nanosilver is preferably from 1 to 5 nm.

Another object of the invention is to provide a method for manufacturingnanosilver-adsorbed fiber where nanosilver is intensively adsorbed onthe surface of synthetic fibers. More practically, the preferred methodcomprises; preparing aqueous solution containing the nanosilver on alarge scale; scouring and washing synthetic fibers; applying the aqueoussolution containing the nanosilver to the surface of the syntheticfibers; adsorbing the nanosilver onto the synthetic fibers using aprocess selected from the group consisting of thermal fixation, highfrequency radiation, bubbling, and combinations thereof; and conductingpost-finishing at 160 to 200° C.

The latter preferred method may further comprise a dyeing step beforethe post-finishing.

Preferably, the thermal fixation is carried out at a temperature from150 to 230° C.

The aqueous solution containing the nanosilver is preferably in anamount of 10 to 100 ppm of the nanosilver.

The step of applying the aqueous solution containing the nanosilver tothe surface of the synthetic fibers is preferable to conducting aprocess selected from the group consisting of spraying, coating, anddipping.

In accordance with a further aspect of a preferred form of the presentinvention, an antibacterial fiber manufactured thereby, in whichantibacterial fiber has the nanosilver has adsorbed thereon in an amountof 0.01 to 0.1 g per 100 g of synthetic fibers

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a device for preparing the aqueous solution containing thenanosilver in accordance with the present invention,

FIG. 2 shows the particle distribution prepared in the presence of ahigh voltage in the aqueous solution containing the nanosilver accordingto the present invention, and

FIG. 3 shows the particle distribution prepared in the presence of a lowvoltage in the aqueous solution containing the nanosilver according toconventional method.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention is described in detail.

First, a method for producing nanosilver on a large scale is describedaccording to an exemplary embodiment of the present invention. Themethod for producing nanosilver on a large scale is provided, based onthe electrolysis of water in which, while high voltage, namely10,000˜300,000 V, is applied to two Ag electrodes (104, 105), thenanosilver on a large scale are generated by keeping up with minuteelectric current between the two electrodes by controlling the height ofthe circuit breaker.

FIG. 1 shows a device for preparing the aqueous solution containing thenanosilver in accordance with the present invention.

More practically, the method for producing nanosilver on a large scaleby using a water electrolysis system comprises:

-   -   loading water so as to immerse the two Ag electrodes;    -   applying voltage of 10,000˜300,000 to two Ag electrodes;    -   moving the circuit breaker upwards or downwards with the        voltage, and thus controlling minutely electric current between        the two Ag electrodes.

The water electrolysis system comprises,

a water reservoir (101) provided with a water inlet valve (102) forintroducing water thereinto and a water outlet (103) valve for drainingthe water therefrom;

the two Ag electrode plates (104, 105) connected to a DC+ electric powersource and a DC− electric power source respectively, the two Agelectrode plates being provided on respective opposite sides of thewater reservoir (101);

a circuit breaker (107) for dividing the water reservoir (101) into twosections, being located of a middle of the water reservoir (101); and

a groove (106) formed by the circuit breaker(107).

It will be readily understood by those skilled in the art that the waterreservoir, the water inlet valve, the water outlet valve, and thecircuit breaker are all electrically insulated.

Generally, it was widely acknowledged that an electric current rises inproportion to voltage, in accordance with the following Formula 1. Whenlow voltage is applied, electric current can be controlled usingcircuits, diodes and the like. However when high voltage is applied,current control is generally impossible.Voltage(V)=Current(I)×Resistance(R)  [Formula 1]

Therefore, the present invention is characterized that while a highvoltage, 10,000˜300,000 V, is applied to electrolysis system, theelectric current control is possible in high voltage. When the highvoltage is applied, it is accomplished that the circuit breaker (107)installed at a middle portion of the water reservoir (101) is movedupwards or downwards to allow only minute electric current between thetwo electrodes. So, the nanosilver on a large scale is generated.

In more detail, when the circuit breaker (107) is absent, electriccurrent flowing through the water reservoir with a certain voltagefollows Formula 1. The other side, the circuit breaker (107) iscontrolled by ½ the height of the water reservoir (101), the electriccurrent flows on the decrease until ½.

Thus, while high voltage, 10,000˜300,000 V is applied to two Agelectrodes, the nanosilver on a large scale is generated by keeping upwith minute electric current between the two electrodes by controllingthe height of the circuit breaker.

The electric current control is conducted until the nanosilver sizebecomes 5 nm or less and preferably 1 to 5 nm. When exceeding 5 nm insize, nanosilver particles lose the property of being easily adsorbed,characteristic of nanosilver, which is generated, because their surfacearea is decreased. In addition, if the electric current amount is notcontrolled to the high voltage, silver ions are not isolated to producenano particles, but silver plating occurs.

FIG. 2 shows the particle distribution prepared in the presence of ahigh voltage in the aqueous solution containing the nanosilver accordingto the present invention. The particle distribution is observed usingscanning electron microscopy. FIG. 2 shows that the nanosilver having asize of 5 nm or less is uniformly distributed. However, FIG. 3 shows theparticle distribution prepared in the presence of a low voltage in theaqueous solution containing the nanosilver according to conventionalmethod. FIG. 3 shows that the particles are non-uniformly distributed,with particle aggregations found therein.

In addition, the nanosilver prepared according to the exemplaryembodiment of the present invention is in a nanosilver solution state sothat the nanosilver particles are uniformly distributed, and thenanosilver can be uniformly and readily coated or adsorbed on syntheticfibers.

Another exemplary embodiment of the present invention is related to amethod manufacturing nanosilver-adsorbed fiber. The method is comprisedof; preparing aqueous solution containing the nanosilver synthesized ona large scale; scouring and washing synthetic fibers; applying theaqueous solution containing the nanosilver to the surface of thesynthetic fibers; adsorbing the nanosilver onto the synthetic fibersusing a process selected from the group consisting of thermal fixation,high frequency radiation, bubbling, and combinations thereof; andconducting post-finishing at 160 to 200° C.

The method may further comprise a dyeing step before the post-finishing.

The nanosilver-adsorbed fiber may be carried out on general cloth types,for example, leather, natural fibers, and synthetic fibers, andpreferably with synthetic fibers.

The term “synthetic fiber” as used herein means generic fiber made fromraw chemical materials, such as polyester, nylon, acryl, etc.Preferably, synthetic fiber has smooth surface such that the nanosilvercan be easily adsorbed thereon, in contrast with natural fibersconsisting of warp and weft. In the case of natural fibers, nanosilveris deeply intercalated into natural fibers, thus antimicrobial activityis poor. The application of the aqueous solution containing thenanosilver to the surface of synthetic fibers may be carried out using aspraying method, a coating method, or a dipping method followed bycoating using a knife or a roll knife.

The antibacterial fiber is preferably adsorbed with nanosilver in anamount of 0.01 to 0.1 g per 100 g of synthetic fibers. According to theexemplary embodiment of the present invention, large amounts ofnanosilver can be adsorbed on the synthetic fibers in comparison toconventional methods. When the amount of the nanosilver adsorbed on thesynthetic fiber is less than 0.01 g, the synthetic fibers haveinsufficient antibacterial activity. On the other hand, if the amount ofthe nanosilver adsorbed on the synthetic fibers is more than 0.1 g, thecost for excessively increases relative to the improvement ofantibacterial effects.

The adsorption of the nanosilver onto the surface of synthetic fibersmay be achieved using various processes. An example among preferredprocesses is a thermal fixation process at 150 to 230° C. The thermalfixation process makes the cloth flexible. Here, when the temperatureduring the process is below 150° C., the surface of raw fiber becomestoo flexible. On the other hand, when the temperature during the processis higher than 230° C., the surface of raw fiber becomes too stiff.Thermal fixation process is needed to be carried out under about 2 atm.

Another process for the adsorption of the nanosilver onto the surface ofthe synthetic fibers uses high-frequency radiation. The high-frequencyradiation process uses an ultrasonic wave frequency that exceeds theupper limit of the range of audio frequencies (16 to 16000 Hz).Generally, ultrasonic waves may be generated by applying an ultrasonicsignal produced in an electric circuit to an ultrasonic oscillator. Theirradiation of ultrasonic waves onto the nanosilver solution producesinnumerable fine voids. The innumerable fine voids are helpful inadsorbing the nanosilver onto the surface of synthetic fibers.

Another process for the adsorption of the nanosilver onto the surface ofthe synthetic fibers may be accomplished through bubbling. In thisprocess, nanosilver particles, ionized by electrolysis, are oscillatedleftwards and rightwards, upwards and downwards, or backwards andforwards by the bubbling. The oscillation of the nanosilver particlesactivates mobility, which is accelerated in the presence of a voltage,so that the nanosilver particles are uniformly distributed over thesynthetic fibers. To carry out the above process using the bubbling, thetarget synthetic fibers are immersed in a separate inner vessel placedinside the water reservoir which has a plurality of openings throughwhich bubbles are generated at a lower portion of the water reservoir.

Next, post-finishing is conducted, in which the synthetic fibers havingnanosilver adsorbed thereon are ironed at 160 to 200° C.

In addition, a dyeing process may be further conducted before thepost-finishing. In the dyeing process, the nanosilver-adsorbed fiber maybe dyed at about 130° C. for 3 to 5 hours with a mixture of a dye and adispersant.

An antibacterial fiber prepared according to the exemplary embodiment ofthe present invention includes nanosilver adsorbed thereon in an amountfrom 0.01 to 0.1 g per 100 g of the synthetic fibers. The syntheticfibers have excellent antibacterial activity because the nanosilverparticles are intensively adsorbed on the surface thereon.

The antibacterial fiber is semi-permanently maintained washingdurability, since the antibacterial fiber was manufactured by easilyadsorptive properties of the nanosilver itself. Test results for washingdurability of the antibacterial fiber made of nanosilver-adsorbed fiberreveals that the nanosilver remained thereon even after 50 washes.

In addition, the nanosilver is intensively adsorbed onto the surface ofthe synthetic fibers. Therefore, the antibacterial fiber according tothe exemplary embodiment of the present invention is excellent toantibacterial activity, and simultaneously can prevent poor perspirationfunctionality and the generation of static electricity.

A better understanding of the present invention may be obtained in lightof the following examples, which are set forth to illustrate, but arenot to be construed to limit the present invention.

EXAMPLE 1

Step 1: Preparation of Aqueous Solution Containing the Nanosilver

As shown in FIG. 1, the device for preparing aqueous solution containingthe nanosilver comprises a water reservoir (101), provided with a waterinlet valve (102) for introducing water thereinto and a water outlet(103) valve for draining the water therefrom; the two Ag electrodes(104, 105) connected to a DC+ electric power source and a DC− electricpower source respectively, the two Ag electrodes being provided onrespective opposite sides of the water reservoir (101); a circuitbreaker (107) for dividing the water reservoir (101) into two sections,being located of a middle of the water reservoir (101); and a groove(106) being formed owing to the circuit breaker (107).

In this device, water was loaded on the water reservoir (101) with thelevel of immersing the two Ag electrodes (104, 105). Next, 30,000 V wasapplied across the two Ag electrodes in the water electrolysis system.The mass production of nanosilver was generated by keeping up withminute electric current between the two electrodes by controlling theheight of the circuit breaker (107) to the water reservoir (101).

The nanosilver thus prepared was proven to have a size of 5 nm or less,with uniform particle distribution as measured using a scanning electronmicroscope (Model LEICA-STEROSCAN440) in FITI Testing & ResearchInstitute of Korea (FIG. 2).

Step 2: Preparation of Antibacterial Fiber

Synthetic fibers were washed with water and scoured at a maximumtemperature of 125° C. so that the synthetic fibers were made clean andneat.

Thereafter, the synthetic fibers were immersed in aqueous solutioncontaining the nanosilver. Here, the temperature of the aqueous solutioncontaining the nanosilver for the adsorption process was maintained at230° C. under a pressure of about 2 atm, so that the nanosilver wasthermally fixed on the surface of the synthetic fibers. In order toensure the thermal fixation of the nanosilver onto the synthetic fibers,ultrasonication was conducted and bubbles were generated to acceleratethe mobility of the nanosilver particles.

Afterwards, a dye and a dispersant were mixed in acetic acid and thesynthetic fibers were dyed at 130° C. for 3 to 5 hours, followed bypost-finishing in which the cloth was pressed at 200° C.

EXAMPLE 2

An antibacterial fiber was manufactured in a same manner to that ofExample 1, with the exception that the circuit breaker (107) wascontrolled to cause the size of nanosilver to be 5 rn or less in thepresence of 300,000 volts (DC+, DC−) in Step 1 of Example 1.

COMPARATIVE EXAMPLE 1

The same procedure as in Example 1 was performed, with the exceptionthat 220 volts (DC+, DC−) was applied in Step 1.

As seen in FIG. 3, the nanosilver prepared in Comparative Example 1 wasobserved to aggregate together, with a non-uniform particle distributionunder a SEM (model: LEICA-STEROSCAN440) in FITI Testing & ResearchInstitute of Korea.

While this invention has been described in connection with certainexemplary embodiments and examples, it is to be understood that thepresent invention is not limited to the disclosed embodiments andexamples, but, on the contrary, is intended to cover variousmodifications included within the spirit and scope of the appendedclaims and equivalents thereof.

As described hereinbefore, the present invention provides a method forproducing nanosilver on a large scale by applying a high voltage inwater electrolysis, and an antibacterial fiber having intensivelynanosilver adsorbed thereon. Furthermore, the nanosilver adsorbed clothis free of the problems possessed by general synthetic fibers, that is,poor perspiration functionality and high static electricity generation,and as well, shows potent suppression against a broad range of bacteriaand microbes.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A method for producing nanosilver on a large scale by using a waterelectrolysis system, comprising: providing two Ag electrode plates;applying a voltage of 10,000˜300,000 to said two Ag electrode plates toproduce a minutely electronic current between said two Ag electrodeplates, said electrode plates being equipped in the water electrolysissystem; and controlling said minutely electronic current between the twoAg electrodes in the water electrolysis system.
 2. The method accordingto claim 1, wherein the method for producing nanosilver on a large scaleby using a water electrolysis system comprising a water reservoir havingtwo opposite sides and a middle and provided with a water inlet valvefor introducing water into said water reservoir and a water outlet valvefor draining the water from said water reservoir; a DC+ electric powersource and a DC− electric power source, said two Ag electrode platesbeing connected to said DC+ electric power source and said DC− electricsource respectively, the two Ag electrode plates being provided onrespective opposite sides of the water reservoir; a circuit breaker fordividing the water reservoir into two sections, being provided in themiddle of the water reservoir; and a groove formed by said circuitbreaker, wherein said method comprises: loading water to immerse saidtwo Ag electrode plates in the water electrolysis system; applying avoltage of 10,000˜300,000 to said two Ag electrode plates; and movingsaid circuit breaker upwards or downwards with the voltage to controlthe minutely electric current between said two Ag electrode plates. 3.The method according to claim 1, wherein the particle size of thenanosilver is 1 to 5 nm.
 4. A method of manufacturingnanosilver-adsorbed fiber comprising: preparing an aqueous solutioncontaining the nanosilver produced according to the method of claim 1;scouring and washing synthetic fibers, said synthetic fibers having asurface; applying the aqueous solution containing the nanosilver to thesurface of said synthetic fibers; adsorbing the nanosilver onto saidsynthetic fibers using a process selected from the group consisting ofthermal fixation, high frequency radiation, bubbling, and combinationsthereof; and conducting post-finishing at 160 to 200° C.
 5. The methodaccording to claim 4, further comprising a dyeing process before thestep of conducting post-finishing at 160 to 200° C.
 6. The methodaccording to claim 4, wherein the thermal fixation process is conductedat a temperature from 150 to 230° C.
 7. The method according to claim 4,wherein the aqueous solution containing the nanosilver is in an amountof 10 to 100 ppm of the nanosilver.
 8. The method according to claim 4,wherein the step of applying the aqueous solution containing thenanosilver to the surface of said synthetic fibers is carried out by aprocess selected from the group consisting of spraying, coating anddipping.
 9. An antibacterial fiber having nanosilver adsorbed thereon inan amount of 0.01 to 0.1 grams per 100 grams of synthetic fibers, andbeing produced according to the method of claim 4.